Add initial handshake reassembly tests.

For now, only test reorderings when we always or never fragment messages.
There's a third untested case: when full messages and fragments are mixed. That
will be tested later after making it actually work.

Change-Id: Ic4efb3f5e87b1319baf2d4af31eafa40f6a50fa6
Reviewed-on: https://boringssl-review.googlesource.com/3216
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/test/runner/conn.go b/ssl/test/runner/conn.go
index 307f61d..86a7b7d 100644
--- a/ssl/test/runner/conn.go
+++ b/ssl/test/runner/conn.go
@@ -69,8 +69,9 @@
 	// DTLS state
 	sendHandshakeSeq uint16
 	recvHandshakeSeq uint16
-	handMsg          []byte // pending assembled handshake message
-	handMsgLen       int    // handshake message length, not including the header
+	handMsg          []byte   // pending assembled handshake message
+	handMsgLen       int      // handshake message length, not including the header
+	pendingFragments [][]byte // pending outgoing handshake fragments.
 
 	tmp [16]byte
 }